This invention relates, in general, to the separation of dry plant tailings into two bulk concentrates. More specifically, it relates to a froth flotation method for the separation of a bulk concentrate which comprises zircon from another bulk concentrate which comprises rutile and ilmenite.
Conventional flotation processes have been used to separate minerals such as copper, molybdenum, zinc, iron, tungsten, and kyanite from waste and other minerals. The minerals are separated by generating air bubbles which selectively attach to the mineral or minerals to be floated. The proper conditions must be present in the flotation process to permit attachment of the mineral to the bubbles. The air bubbles, together with the attached group, rise to the surface to form a froth which is removed. However, if the weight of the particles is too high or the forces of attachment are too weak, the minerals will drop from the bubbles and the minerals will not become part of the froth. Therefore, the weight of the particles must be low enough and the forces of attachment strong enough to permit the bubbles to rise while carrying the mineral with it.
It is known in froth flotation technology to use anionic-type promoters to provide proper conditions for the attachment of minerals to air bubbles. For example, an anionic-type promoter has been used to condition phosphorus-bearing minerals for attachment to air bubbles. See, for instance, U.S. Pat. Nos. 2,557,455 and 3,482,688. It is also known to use depressants in froth flotation processes for depressing the minerals which form the sink product. For example, U.S. Pat. No. 2,497,863 is directed to subjecting pulp to a processed starch product to depress the minerals in the pulp.
In the conventional froth flotation systems, silicates are separated from the titanium values. Titanium values are present in ilmenite and rutile. Ilmenite is a compound of ferrous oxide and titanium dioxide and rutile is a compound of titanium dioxide. After the separation of the titanium values, the titanium values are retained as the desired product and the silicates are discarded.
In U.S. Pat. No. 2,904,177 a flotation method is used for the removal of silicates from an ilmenite ore. The silicates present in the ilmenite ore are garnet, feldspar, hornblende and augite. The silicates are removed by grinding the ore to -60 mesh size; preparing an aqueous pulp with the ground ore; acidifying the pulp with hydrofluoric acid; adding starch to the pulp to depress the titanium values present in the ilmenite ore; adding to the pulp a cationic amine flotation agent; and subjecting the treated pulp to a froth flotation. According to this patent, the titanium values form the desired product and the silicates are discarded. In this patent, the pH is lowered before subjecting the treated pulp to froth flotation to remove the feldspars and other silicates. Although this method has been used to recover titanium values, this conventional process has not been used to recover a zircon float product from a rutile/ilmenite sink product.
It has now been found that zircon, a valuable mineral, can be effectively recovered from tailings by means of froth flotation. In the present invention, dry plant tailings are used which comprise zircon, aluminum minerals, quartz, ilmenite and rutile from which tailings the zircon and the rutile/ilmenite can be recovered. Thus, in the present invention both the zircon bulk concentrate and rutile/ilmenite bulk concentrate are recovered as final products and are further cleaned as required by dry processing to marketable grade products.
It is an advantage of the present invention that high concentrations of two desired bulk products can be recovered from dry plant tailings. Other advantages of the present invention are that the flotation process provides a means for recovering fine titanium and zircon values that are not efficiently recovered by conventional dry processing. Further, since these plant tailings are rejects from the conventional dry processing, it is likely that treating them again by the same dry methods would be inefficient, and hence a new process is required to allow the tailing to be recovered. It has been determined that it is advantageous to separate two bulk products in a froth flotation process by manipulating the surface charges on the minerals of the dry plant tailings.